The present invention relates to a method for filling a tank with pressurized gas.
The invention relates more particularly to a method for filling a tank with pressurized gas, particularly hydrogen in the tank of a vehicle, using a filling station that comprises a plurality of buffer containers for containing the pressurized gas and filling the tank through successive pressure balancing phases and a device for generating a pressurized gas and for filling said buffer containers from a fluid source.
The rapid filling (typically in less than 15 minutes) of tanks under high pressure (above 700 bar in particular) mounted on vehicles (for example hydrogen gas for vehicles equipped with fuel cells) is conventionally carried out by successive pressure balancings with a plurality of buffer containers at high pressure. This “cascade” filling is conventionally obtained by providing a succession of pressure balancings between, on the one hand, the target tank to be filled and, on the other hand, buffer containers under increasing pressure (for example 200 bar then 300 bar then 450 bar then 850 bar).
This well known method is described abundantly in the literature, particularly for natural gas or hydrogen applications.
This known method for filling by pressure balancings nevertheless requires a large number of high pressure containers. This accordingly increases the risks of leakage and the quantity of gas which must be stored on a site. Typically, the quantity of gas immobilized by this method is about three times the average daily consumption used by the station. This may require the filing of applications for special permits in the case in which the gas is inflammable or hazardous.
Furthermore, by this method, for successive fillings of several vehicles without excessive waiting time, it is necessary to increase the number of high pressure buffer containers available and therefore necessarily the size of the filling station.
According to another known filling technology called “slow filling” (for example longer than 15 minutes), the gas is introduced into the tank directly from a low pressure hydrogen source via a compressor.
This “direct compression” filling method does not in fact permit the filling of tanks in less than 15 minutes unless very large compressors (or cryogenic pumps) are used, requiring very high electric power (for example about 70 kW for a liquid pump and more than 300 kW for a compressor).